As the number of samples to be analyzed continue their ever increasing pattern, the importance of automated chemical analysis procedures continues to increase as well. So far for liquid-phase analysis, the major emphasis has been on continuous flow systems. Segmented Continuous Flow Analysis (SCFA) as introduced by Skeggs in 1957 (Am. J. Clin. Pathol., 28, pp. 311-322) was commercialized subsequently by the Technicon Corporation and proved so extraordinarily successful that for years automated liquid-phase analysis was synonymous with the trade name of the Technicon instrument, the Autoanalyzer. More recently, Flow Injection Analysis (FIA), also a continuous flow procedure but without segmentation, has proved to be a formidable contender to SCFA (see U.S. Pat. No. 4,022,575 to Hansen and Ruzicka). Despite the unique ability of FIA to provide reproducible dispersion profiles, the overwhelming majority of FIA applications continue to involve single-point measurement (typically peak height). In such a case, FIA is merely an analog of SCFA.
Liquid-phase analysis can be automated without continuous flow. One example of this is represented by the DigiChem 4000 series analyzer marketed by Ionics, Inc. In this analyzer, the sample and up to five reagents are delivered to a reaction cell by steppermotor driven syringes The contents of the cell are then mixed by spinning the cell. Higher speed spinning is used to empty the cell after in-situ detection, e.g., by placing a pH probe in the cell. Although a volumetric resolution of 0.12 microliter is possible with small volume syringes, the total measurement volume must be much higher overall, it cannot be considered a microscale analyzer. However, the concept is sufficiently unique and the potential sufficiently diverse that the instrument is now discussed in textbooks such as "Process Analyzer Technology" published by Wiley in New York in 1986 and authored by K. J. Clevett as well as "Principles of Instrumental Analysis", 3rd edition, published by Saunders in New York in 1985 and authored by D. A. Skoog.
In addition, Kallos, in U.S. Pat. No. 4,042,326, describes an automated batch analysis system where a volume of sample and a volume of reagent (or reagents) are added to a reaction chamber to form a reaction product that is subsequently analyzed. The system of Kallos also cannot be considered a microscale analyzer. Some clinical type analyzers (such as the ones described in "Automatic Chemical Analysis" published by Horwood in Sussex, England in 1975 and authored by Foreman et al.) can be considered microscale systems but so far do not find much use in non-clinical laboratories, probably because they are complex and costly systems, e.g., they generally use many test tube-like reaction chambers and transport the chambers from station to station to receive samples and reagents.